1. Field of the Invention
The present invention relates to hand held electric screwdrivers and, more particularly, to a screw driving device for driving screws, of varying head configurations and sizes, into work surfaces in a fully automatic and controlled manner.
2. Description of the Prior Art
The process of fastening sheet construction materials is generally achieved using hand held electrical screw guns which are manually fed with screws, one by one. Current proposals to improve this procedure through partial automation generally utilize a manually operated ratchetting mechanism to feed screws, attached in series to a belt, into position in front of a screwdriver bit. The screwdriver is then actuated and manually pushed forward to engage the screw and drive it into the work surface. U.S. Pat. No. 5,109,738 issued on May 5, 1992 to Marian et al. and U.S. Pat. No. 5,167,174 issued on Dec. 1, 1992 to Fujiyama et al. both describe such belt fed screw driving machines. U.S. Pat. No. 5,154,242 issued on Oct. 13, 1992 to Soshin et al. describes a manually fed screwdriver with a multi-stage tightening torque control. This screwdriver allows for a high speed screw driving phase and a slow speed final tightening phase; it also controls torque by monitoring motor temperature to correct for variations in the magnetic characteristic of the motor due to temperature variations. All control functions in the machine are microprocessor based.